1. Field of the Invention
This invention relates to a work-supporting deck for use in machine tools, particularly in cutting machines for cutting flat stock, which deck comprises vacuum aspirators, which serve to support and retain a workpiece and carry suction cups, which are adjustable in height by actuators.
2. Description of the Prior Art
Work-supporting decks having a work-supporting surface, at which a vacuum can be applied, have proved satisfactory for use in the processing of flat stock, such as the trimming or contour milling of metal plates and parts of wood, and particularly of monolayer plastic blanks or multilayer plastic blanks (composites), because the two-dimensional workpieces can reliably be retained on the work-supporting surface by the applied vacuum substantially independently of their geometric configuration. But in order to avoid damage to such so-called vacuum decks, they must be provided with cover plates which support the workpieces and consist of an air-permeable material or of contour templates provided with suitable gaskets. But contour templates involve a substantial expenditure and must conform to specific workpieces so that their use is restricted. The porous cover plates of foamed plastic also cannot be satisfactory because furrows will be cut into the cover plate as it is penetrated by the tool during its processing operation and such furrows will adversely effect the application and action of the vacuum which is required for this reason it is necessary to use a tool which laterally protrudes over the workpiece only to the smallest possible extent and to cover the workpiece at its edges with plastic films so that the utilization of the tool is decreased and the films must be handled in a complicated manner.
In EP-A-0069 230 it has already been suggested to provide a work-supporting deck with several vacuum aspirators and to support the workpieces only by the suction cups of said aspirators rather than on a continuous work-supporting surface. But the workpiece cannot be retained as desired by the known vacuum aspirators unless they engage the workpiece at predetermined points so that each aspirator must individually be laterally adjusted and the work-supporting decks provided with said aspirators can be used only to support workpieces having a predetermined shape. Besides, the workpiece is supported only at a few points so that the processing of the workpiece gives rise to vibration, which often preclude the use of mechanical means for additionally fixing the workpiece.